Deposition method for wiring thin film

ABSTRACT

An Al 3 Ti film having a large amount of dissolved Si is deposited on a semiconductor substrate to form a laminate with an Al wiring film, and heat treatment is performed at a temperature of at least 400° C., to thereby absorb excessive Si into the Al 3 Ti film and to so prevent the occurrence of Si nodules. By depositing Al film at a temperature of at least 400° C. at the time of depositing the Al wiring film on the Al 3 Ti film, excessive Si is caused to be absorbed in the Al 3 Ti film. Further, at the time of depositing a Ti film on the semiconductor substrate and depositing the Al wiring film, the Al film is deposited at a temperature of at least 400° C., there is reaction between the Ti film within the laminate, causing an Al 3 Ti film to be produced, and excessive Si is absorbed in the Al 3 Ti film produced.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of application Ser. No. 09/754,264,filed Jan. 5, 2001, which is hereby incorporated by reference in itsentirety for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor element manufacturingmethod and to the construction of an element manufactured using themethod, and particularly to a deposition method for a thin film used aswiring and a laminated construction for a thin film deposited using thismethod.

2. Description of the Related Art

In the case of forming an element on a conventional semiconductorsubstrate, a wiring thin film deposition method as shown in FIGS. 1-3 iscarried out. First of all, an insulating film 2 (for example, SiO₂ BPSG)is deposited on a semiconductor substrate 1 typically of a material suchas silicon, and a barrier layer 3 (for example, Ti, TiN or a laminate ofthe two) is deposited. Next, an Al film is deposited with thesemiconductor substrate heated to 150-400° C., by a sputtering methodusing an Al—Si—Cu target having Si added to 0.05-1.0% which is at leastthe solution limit of Al.

Here, Si is added to improve EM (electromigration) resistance. Also, thereason for heating the semiconductor substrate at the time of Aldeposition is to increase the size of the Al grains (crystal grain) toincrease EM resistance, and to improve step coverage. Next, anantireflection membrane (ARM) 5 that is, for example, Ti, TiN or alaminate of the two, is deposited, preferably by performing aphotolithography process. After that, wiring is patterned using a wellknown photolithography method or etching method.

However, with the Al thin film sputter deposited using an Al—Si—Cutarget having Si added to at least the solution limit of Al as describedabove, there are the following problems. Specifically, at the time ofdepositing the Al film, deposited Si particles 6 are dissolved in Al dueto the high heating temperature of the deposition, and in a process ofcooling the wafer gradually after deposition from the depositiontemperature there is a nucleus of remaining Si that could not bedissolved. Recrystallization growth of the temporarily dissolved Sistarts, as a result of which an enormous Si deposit 7 is formed (referto FIG. 4(1)-(3). This Si deposit 7 deposited in the Al film is notremoved by etching gas in the Cl₂ family that is normally used at thetime of etching the Al film in a subsequent step, and as a resultremains as an Si residue. As shown in FIG. 5, this Si residue 8unfortunately acts as a mask at the time of etching the Al underneaththe residue. Because of this, pattern defects arise, and if the size ofthe Si residue becomes larger than an interval between wires in thewiring pattern this will cause shorting between wires.

SUMMARY OF THE INVENTION

An object of the present invention is to solve the problem of Si nodulesthat occurs when depositing an Al wiring film with a sputter methodusing an Al—Si—Cu target, and to provide a more stable deposition methodfor a wiring thin film that prevents Si nodules occurring.

With the present invention, in order to achieve the above object, thereis a wiring thin film deposition method comprising the steps ofdepositing a Ti film on a semiconductor substrate, and depositing anAl—Si—Cu film on the Ti film at a temperature of at least 400° C.According to this method, it is possible to achieve the above describedobject because an Al₃ film is formed between layers of the Ti film andthe Al—Si—Cu film and excess Si is absorbed.

There is also provided a wiring thin film deposition method includingthe steps of depositing a Ti film on a semiconductor substrate,depositing an Al—Si—Cu film on the Ti film, and annealing thesemiconductor substrate at a temperature of at least 400° C. The basicconcept of this method is absorption of Si by an Al₃Ti film.

There is also provided a wiring thin film deposition method comprisingthe steps of depositing a Ti film on a semiconductor substrate,depositing an Al₃Ti film on the Ti film, and depositing an Al—Si—Cu filmon the Al₃Ti film at a temperature of at least 400° C., and the basicconcept of this method is as described above.

There is also provided a wiring thin film deposition method comprisingthe steps of depositing a Ti film on a semiconductor substrate,depositing an Al₃Ti film on the Ti film, depositing an Al—Si—Cu film onthe Al₃Ti film, and annealing the semiconductor substrate at atemperature of at least 400° C., and the basic concept of this method isas described above.

Still further, there is provided a wiring thin film deposition methodcomprising the steps of depositing a Ti film on a semiconductorsubstrate, depositing an Al—Si—Cu film on the Ti film, depositing anAl₃Ti film on the Al—Si—Cu film, and annealing the semiconductorsubstrate at a temperature of at least 400° C., and the basic concept ofthis method is also as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a first cross sectional drawing showing a process of therelated art.

FIG. 2 is a second cross sectional drawing showing a process of therelated art.

FIG. 3 is a third cross sectional drawing showing a process of therelated art.

FIGS. 4-1 through 4-3 show the mechanism of the related art process.

FIG. 5 shows the disadvantages of the related art.

FIG. 6 is a first cross sectional drawing showing a process of a firstembodiment of the present invention.

FIG. 7 is a second cross sectional drawing showing a process of thefirst embodiment of the present invention.

FIG. 8 is a third cross sectional drawing showing a process of the firstembodiment of the present invention.

FIG. 9 is a first cross sectional drawing showing a process of a secondembodiment of the present invention.

FIG. 10 is a second cross sectional drawing showing a process of thesecond embodiment of the present invention.

FIG. 11 is a first cross sectional drawing showing a process of a thirdembodiment of the present invention.

FIG. 12 is a second cross sectional drawing showing a process of thethird embodiment of the present invention.

FIG. 13 is a third cross sectional drawing showing a process of thethird embodiment of the present invention.

FIG. 14 is a first cross sectional drawing showing a process of a fourthembodiment of the present invention.

FIG. 15 is a second cross sectional drawing showing a process of thefourth embodiment of the present invention.

FIG. 16 is a first cross sectional drawing showing a process of a fifthembodiment of the present invention.

FIG. 17 is a second cross sectional drawing showing a process of thefifth embodiment of the present invention.

FIG. 18 is a first cross sectional drawing showing a process of a sixthembodiment of the present invention.

FIG. 19 is a second cross sectional drawing showing a process of thesixth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment of the present invention will now be described indetail using FIG. 6 to FIG. 8. First of all, an insulating film 21 (forexample SiO₂, BPSG) is deposited on a semiconductor substrate 20. Next,a Ti film 22, for example, is deposited to a thickness of 50 nm, as abarrier layer. An Al film 24 is then deposited to a thickness of 400-800nm by a sputter method using an Al-1.0% Si-0.5% Cu target. Thetemperature when this Al film is deposited is at least 400° C.

In this way, if the Al film is deposited under high temperatureconditions, reaction between the Al and Ti is promoted to form an Al₃Tialloy layer 24. It is confirmed that the Al₃Ti contacting this Alsurface absorbs Si within the Al. For example, the extent of Sidissolved in the Al₃Ti at 450° C. is about 15 weight %, which isextremely high.

Accordingly, with this embodiment, diffusion of Si into the Al₃Ti ispromoted and the amount of Si in the Al is reduced, so that there is noSi deposit due to recrystallization. Since this Al₃Ti alloy layer 24 isformed, the temperature of the semiconductor substrate at the time ofdeposition of the Al film is at least 400° C., and the Al film isdeposited. After that, a TiN film, for example, is deposited to athickness of 50 nm, as an antireflection film, and then patterning isperformed using a well known method.

As described above, according to the present invention, in the casewhere the barrier layer is Ti, by depositing an Al film with a highwafer temperature of at least 400° C., reaction between Al and Ti ispromoted, and an Al₃Ti alloy layer is formed. The Al₃Ti contacting theAl surface absorbs Si in the Al film due to the high temperatureprocessing at the time of depositing the Al film. Accordingly, theamount of Si on the Al film is reduced, and it is possible to suppressre-crystallization of Si during a process of cooling the wafer graduallyfrom the film formation temperature. In this way, it is possible toprevent the formation of an enormous Si deposit, and by preventingpattern defects at the time of Al etching that would normally be causedby such an Si deposit it is possible to prevent short circuits betweenwires.

Second Embodiment

A second embodiment of the present invention will now be described usingFIG. 9 and FIG. 10. First of all, an insulating film 31 (for exampleSiO₂, BPSG) is deposited on a semiconductor substrate 30. Next, a Tisingle layer film 32, for example, is deposited to a thickness of 50 nm,as a barrier layer. An Al film 33 is then deposited to a thickness of400-800 nm by a sputter method using an Al-1.0% Si-0.5% Cu target. Then,a TiN film is deposited to a thickness of 50 nm, as a barrier layer. Thedeposition conditions for each of the films can be the same as in therelated art.

Once deposition of the above films is completed, the semiconductorsubstrate is annealed at a high temperature of at least 400° C. As aresult of this annealing process reaction between the Al and Ti ispromoted, and an Al₃Ti alloy layer is formed. It was confirmed thatAl₃Ti coming to contact with this Al surface absorbed Si within the Al,as described above. Accordingly, with this embodiment diffusion of Siinto the Al₃Ti is promoted and the amount of Si in the Al is reduced,making it possible to prevent any Si deposit due to recrystallization.

As described above, according to the second embodiment, after depositionof an anti-reflection film has been completed in the case of a Tibarrier layer, reaction between Al and Ti is promoted, by performingannealing processing at least 400° C., and an Al₃Ti alloy layer isformed. Since the temperature of the Al₃Ti alloy layer 35 coming tocontact with this Al surface is high at the time of annealing, Si in theAl is absorbed. As a result, the amount of Si in the Al is reduced, andit is possible to suppress recrystallization growth of Si in a step ofcooling the semiconductor substrate from the film depositiontemperature. In doing this, it is possible to prevent formation of anenormous Si deposit, and by preventing pattern defects at the time of Aletching caused by the Si deposit it is possible to prevent shortsbetween wires.

Third Embodiment

A third embodiment of the present invention will now be described usingFIG. 11, FIG. 12 and FIG. 13. First of all, an insulating film 41 (forexample SiO₂, BPSG) is deposited on a semiconductor substrate 40. Next,a Ti film 42 is deposited to a thickness of 50 nm, as a barrier layer.The film formation conditions up to the barrier layer can be the same asin the related art. With this embodiment, before deposition of Al, anAl₃Ti film 43 is previously deposited to a thickness of 10-20 nm by asputter method using an Al₃Ti target. An Al film 44 is then deposited toa thickness of 400-800 nm at a deposition temperature of at least 400°C. by a sputter method using an Al-1.0% Si-0.5% Cu target. The reasonfor making the deposition temperature of the Al film at least 400° C. isto promote absorption of Si into the Al₃Ti. After that, a TiN film isdeposited to a thickness of 50 nm as an ant-reflection film.

As described above, according to the third embodiment, by previouslydepositing the Al₃Ti film before Al deposition using an Al₃Ti target,and then depositing the Al film at a high temperature of at least 400°C., the Al₃Ti film coming into contact with the Al absorbs Si in the Alat the time of film formation, which reduces the amount of Si in the Al,and it is possible to suppress Si recrystallization growth in a step ofcooling the wafer from the film formation temperature. In this way, itis possible to prevent formation of an enormous Si deposit, and bypreventing pattern defects that would be caused by the Si deposit at thetime of Al etching it is possible to prevent shorts between wires.

Fourth Embodiment

A fourth embodiment of the present invention will now be described usingFIG. 14 and FIG. 15. First of all, an insulating film 51 (for exampleSiO₂, BPSG) is deposited on a semiconductor substrate 50. Next, a Tifilm 52 is deposited to a thickness of 50 nm, as a barrier layer. Thefilm formation conditions up to the barrier layer can be the same as inthe related art. With this embodiment, before deposition of Al, an Al₃Tifilm 53 is previously deposited to a thickness of 10-20 nm by a sputtermethod using an Al₃Ti target. An Al film 54 is then deposited to athickness of 400-800 nm by a sputter method using an Al-1.0% Si-0.5% Cutarget. After that, a TiN film 55 is deposited to a thickness of 50 nmas an anti-reflection film. After deposition of the above films has beencompleted, the semiconductor substrate is annealed at a high temperatureof at least 400° C. in order to promote absorption of Si into the Al₃Tifilm.

In this way, according to the fourth embodiment, the Al₃Ti film isdeposited before Al deposition using an Al₃Ti target, and afterdepositing the antireflection film annealing is carried out at a hightemperature of at least 400° C. in order to promote absorption of Siinto the Al₃Ti film. As a result of this annealing, the Al₃Ti filmcoming into contact with the Al absorbs Si in the Al film, which reducesthe amount of Si in the Al, and it is possible to suppress Sirecrystallization growth in a step of cooling the wafer from the filmformation temperature. In this way, it is possible to prevent formationof an enormous Si deposit, and by preventing pattern defects that wouldbe caused by the Si deposit at the time of Al etching it is possible toprevent shorts between wires.

Fifth Embodiment

A fifth embodiment of the present invention will now be described usingFIG. 16 and FIG. 17. First of all, an insulating film 61 (for exampleSiO₂, BPSG) is deposited on a semiconductor substrate 60. Then, a Tifilm 62 is deposited as a barrier layer. Next, an Al film 63 isdeposited on the barrier layer 62 by a sputter method using Al-0.8%Si-0.3% Cu target. The film formation condtions up to the Al film can bethe same as in the related art. With this embodiment, after depositionof Al, an Al₃Ti film 64 is deposited to a thickness of 10-20 nm by asputter method using an Al₃Ti target. After that a TiN anti-reflectionfilm is deposited to a thickness of approximately 50 nm in the same wayas in the related art After deposition of the antireflection film hasbeen completed, annealing is carried out at a high temperature of atleast 400° C. in order to promote absorption of Si into the Al₃Ti film.

As described above, according to the fifth embodiment, by depositing theAl₃Ti film 64 by a sputter method using an Al₃Ti target after Al filmformation, and carrying out annealing at a high temperature of at least400° C. in order to promote absorption of Si into the Al₃Ti afterdeposition of the antireflection film, the Al₃Ti film coming intocontact with the Al is made to absorb Si in the Al film, which reducesthe amount of Si in the Al, and it is possible to suppress Sirecrystallization growth in a step of cooling the wafer from the filmformation temperature. In this way, it is possible to prevent formationof an enormous Si deposit, and by preventing pattern defects that wouldbe caused by the Si deposit at the time of Al etching it is possible toprevent shorts between wires.

Sixth Embodiment

A sixth embodiment of the present invention will now be described usingFIG. 18 and FIG. 19. First of all, an insulating film 71 (for exampleSiO₂, BPSG) is deposited on a semiconductor substrate. Next, a Ti film72 is deposited to a thickness of 50 nm, as a barrier layer. An Al film73 is deposited on the Ti film by a sputter method using an Al-0.8%Si-0.3% Cu target. The film formation conditions up to the Al film canbe the same as in the related art. With this embodiment, afterdeposition of Al, an Al₃Ti film 74 is deposited to a thickness of 10-20nm by a sputter method using an Al₃Ti target. Deposition at this time isperformed at a high temperature of at least 400° C. After that a TiNant-reflection film 75 is deposited to a thickness of about 50 nm in thesame way as in the related art.

As described above, according to the sixth embodiment, the Al₃Ti film 74is deposited at a temperature of at least 400° C. by a sputter methodusing an Al₃Ti target, after Al film formation. By carrying out theAl₃Ti deposition at the high temperature of at least 400° C. in order topromote absorption of Si into the Al₃Ti, the Al₃Ti film coming intocontact with the Al is made to absorb Si in the Al film, which reducesthe amount of Si in the Al, and it is possible to suppress Sirecrystallization growth in a step of cooling the wafer from the filmformation temperature. In this way, it is possible to prevent formationof an enormous Si deposit, and by preventing pattern defects that wouldbe caused by the Si deposit at the time of Al etching it is possible toprevent shorts between wires.

1: A method of forming a wiring film, the method comprising: providing asubstrate; depositing a Ti layer over said substrate; depositing an Allayer on said Ti layer using an Al—Si—Cu target; annealing the substrateat a temperature of at least 400° C. after said depositing an Al layerto form an Al₃Ti layer on said Ti layer and to promote absorption of Sifrom said Al layer into said Al₃Ti layer; and pattern etching said Allayer after said annealing. 2: The method according to claim 1, furthercomprising forming an insulating layer between said substrate and saidTi layer. 3: The method according to claim 1, further comprisingdepositing a TiN layer on said Al layer. 4: The method according toclaim 1, wherein a thickness of the deposited Al layer is 400-800 nm. 5:The method according to claim 2, wherein said insulating layer is anSiO₂ layer or a BPSG layer.